Modern vehicles often incorporate one or more drivetrain modes for providing power from an engine to the driven wheels. For example, a vehicle with only a two-wheel drive system, or 4×2 mode, may provide power via one or a series of rotating shafts to two wheels of the vehicle. Vehicles such as compact cars may use a front wheel drive system with power provided to the two front wheels. In other, often larger vehicles, it is often desirable to incorporate both two-wheel drive and four-wheel drive driving modes, wherein power may be selectively distributed to two wheels in one mode and four wheels in another mode. Vehicles of different sizes often incorporate two-wheel drive of the rear wheels and four-wheel drive for the purpose of enabling better handling during varying traction conditions while still being able to switch to two-wheel drive to reduce fuel consumption and reduce wasted power.
For vehicles with switchable drive modes, devices and systems are needed for engaging and disengaging drivetrain components such as axles and shafts. As such, disconnect assemblies are used that often involve a form of clutch that can move to connect or disconnect two rotatable components such as two shafts. The disconnect assemblies can be placed in a variety of areas in the drivetrain of a vehicle, including at the wheel ends, at one or more axles, or along one of the drive shafts. Through the use of disconnect systems, vehicles can be made more versatile by having the ability to switch between different drive modes depending on the driving conditions and operator desire.
In some powertrain disconnecting systems, vacuum directed from the vehicle engine is used as the motive or actuating force that powers the disconnecting systems. In particular, the disconnecting system actuators may be powered by the vacuum. In many systems, the vacuum is directed via a passage from the intake manifold of the gasoline-fueled engine. Due to this, the vacuum level, or amount of force or pressure available from the vacuum, may vary as engine throttle settings change along with engine load. For turbocharged diesel-fueled engine systems, vacuum may be generated by an auxiliary pump. For both gasoline and turbocharged diesel engine systems, the vacuum level (amount of pressure available) may be limited or vary due to the effects of altitude. Furthermore, temperature changes can also cause pressure fluctuations in the vacuum level, thereby causing fluctuations in movement of the disconnect actuator which may result in undesirable movement of disconnect components such as the diaphragm and clutch components. Additionally, in some vehicles vacuum may not be readily available since various vehicle accessory systems may not be powered by vacuum, or the vehicle may be designed to remove engine intake connections such as vacuum lines in order to enhance engine control and performance. Finally, vacuum-powered powertrain disconnect systems are becoming less desirable with more advanced vehicle design. As such, powertrain disconnect systems are needed that are powered by sources other than vacuum and feature designs conducive to modern vehicle systems. The inventors herein have recognized the above issues and developed various approaches to address them.
Thus in one example, the above issues associated with vacuum powered disconnects may be at least partially addressed by a motorized disconnect assembly, comprising: a shifter assembly including an undulating gear track undulating between two ends of the shifter assembly in a direction of a rotation axis of an interfacing, first shaft, the gear track trapped between fixed cam guides. In this way, a compact disconnect assembly is provided that is powered by an electric motor located on-board the disconnect assembly and does not rely on vacuum power. Also, the undulating gear track may allow the electric motor to be driven in only a single direction during one or more particular shift commands or modes, allowing the shifter assembly to move back and forth along an axial direction.
In another example, the motorized disconnect assembly may be placed in a self-contained housing and disposed between two rotating components. This may allow for a more compact design compared to other disconnect assemblies. Also, as described in further detail later, the placement of the disconnect housing may protect and substantially isolate internal components from external contamination such as dust and unwanted grease and/or oil. The isolation of inner components may aid in increasing the durability and longevity of the disconnect assembly, thereby reducing repair and replacement costs for its continued operation.
The proposed powertrain disconnect system may include an electric motorized disconnect that may alleviate the aforementioned issues associated with vacuum-powered disconnects. An electric motor-powered disconnect may not fluctuate as vacuum-powered disconnects do. Furthermore, the disconnect assembly also features a shifter assembly that rotates and moves axially via a worm drive. The axial movement may be caused by a worm gear engaging an oscillating (non-planar or curved) gear track that in turn moves the shifter assembly along the axial direction as the shifter assembly rotates. This movement may be used to cause engagement and disengagement between two rotating components, such a drive shafts and/or axles.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.